The present invention relates to an optical memory, such as an optical disk and an optical card for recording, reproducing and erasing information using a laser beam or the like, and also to an information processing apparatus for using said optical memory.
Also, the present invention relates to an optical memory and an information processing apparatus used only for reproducing information previously stored in said optical memory.
In an optical recording medium, such as an optical disk, a laser beam or the like is collected until it reaches a diffraction limit in order to record, reproduce and erase information. As a result, the information can be recorded on such optical recording medium at extremely high density.
Thus, such large capacity-memories have been mainly developed as auxiliary memories for large-scale computers.
On the other hand, small-sized portable computers such as, for instance, lap-top computers, have been marketed very recently, and floppy disks are being presently utilized as typical changeable medium memories for such small-sized computers. However, the memory capacity of the typical floppy disk is rather small. Thus, a strong demand has been currently made for such a high-density memory with a changeable recording medium instead of the floppy disk.
In response to such demands, various types of optical memories have been proposed.
For instance, as to compactness, optical cards having a higher degree of portability have been proposed. Although an optical card has the advantage that a higher portability may be expected with a compact size and a large memory capacity, there is a difficulty that the data transfer speed thereof is very much slower than that of a rotation type optical disk, because both the data recording and reproducing operations are performed with a linear scanning. To solve the above-described difficulty, which is inherent to the optical card, one proposal has been made as described JP-A-60-79581, which is directed to a card in which there is provided a rotation type recording medium sheet, for instance, an optical disk having a thickness substantially equal to the thickness of a conventional cash card. Since data is recorded on the rotation type recording medium sheet in this optical card, there is a particular advantage that a higher data transfer speed may be achieved, as compared with that of the conventional optical card. As a result, this proposed improvement can overcome the above-described problem inherent in the conventional optical card, i.e., low data transfer speed, while other merits such as better portability and easy handling of the typical optical cards are maintained.
On the other hand, the conventional optical disk is mounted within a cartridge case, the shutter capable of being opened/closed is provided on a portion of the case within the disk drive, and the laser light beam is irradiated onto the disk. The reason why such an optical disk is mounted within a cartridge case, is to prevent dust from being deposited on the disk surface and also to realize easy mounting operations in the use of this cartridge case. However, generally speaking, the thickness of a hard cartridge case is rather large and there is a drawback that the total weight of the cartridge case becomes heavy. Therefore, there is a demand to make the cartridge case thinner and lighter. Nevertheless, to make a thinner cartridge case, an optical disk substrate having a typical thickness of 1.2 mm must be made thinner. In general, when a thickness of a substrate becomes thinner, an adverse influence caused by a laser scattering (due to dust deposited on the substrate surface ) becomes greater. As a result, this may cause, in turn, other various drawbacks that the laser power during the recording operation is lowered and read-out errors during the reproducing operation may occur. Consequently, the presently available shutter type cartridge case can hardly prevent a dust problem. As one of the possible dust preventing methods, a mechanism has been proposed in JP-A-64-25378 dust is collected by controlling air flows. However, there is no clear description that such a dust preventing method may be similarly applied to the above-described thinner optical disk substrate. For instance, as described in another publication, JP-A-64-30087, a dust preventing idea has been proposed in which the optical disk is sealed within the cartridge case by way of the shutter and the laser light is irradiated through the cover glass formed on the cartridge case onto the surface of the optical disk.
In accordance with the conventional dust preventing ideas as described in JP-A-60-79581 and JP-A-64-30087, to achieve sufficient dust protection with the thinner memory medium, the optical disk built in the cartridge case must be highly sealed, or sufficiently sealed within the cartridge case. To this end, there exists a particular advantage that the laser light is projected via the case cover onto the disk surface, which is different from the conventional system in which the laser light is directly irradiated onto the disk surface.
When, as described above, the optical disk is built in the cartridge case, this case is spatially separated from the optical disk so that a space is necessarily formed therebetween. Air fills this space under normal use. On the other hand, in case that a flexible thin optical disk as described in JP-A-60-79581 and JP-A-64-30087 is mounted so as to be rotated within a case, space intervals between the optical disk and case are continuously varied due to face vibrations of this optical disk, which occur during rotation of the optical disk. In particular, since the face vibrations of the mechanically flexible optical disk become great, such great face vibrations may be suppressed by employing a stabilizer plate as described in JP-A-64-30087. However, it is very difficult to prevent the rotating optical disk from hitting the stabilizer plate, and so the rotating optical disk is set in close proximity to the stabilizer plate for purposes of establishing an air bearing effect therebetween.